The global rollout of the fifth-generation (5G) of mobile cellular communications is currently underway, with the promise of revolutionizing the communications landscape by improving user experience with interactive and haptic communications, and enabling machine-oriented services that are fundamental for industry automation, intelligent transportation, e-health, among others. While the future of 5G and beyond 5G (B5G) networks looks bright, the design of such networks continues to be a challenging task due to the stringent performance requirements that these networks should meet to deliver ultra-reliable and low-latency services with enhanced mobility. In particular, the optimization of the radio access network of 5G, as well as its redesign toward the transition to sixth-generation (6G) networks, call for the development of proper channel models that serve as benchmarks for system analysis.